Rust preventive aviation oil



United States Patent RUST PREVENTIVE AVIATION 01L Roy A. Westlund, Jr.,Linden, and Robert W. Scott, Westfield, N. J., assignor to Esso Researchand Engineering Company, a corporation of Delaware No Drawing.Application October 1, 1954 Serial No. 459,849

1 Claim. (Cl. 252-56) This invention relates to lubricants and moreparticularly relates to a novel lubricant composition which acts as anengine lubricant at normal engine operating temperatures and which gelsto a plastic-type rust preventive upon cooling.

In the aviation industry it is frequently necessary to store aviationengines for extended periods of time. This storage may be occasioned bythe temporary retirement from service of the aircraft, long periods ofdelay prior to engine overhaul, or for numerous other reasons. In thecase of military aircraft, for example, the storage period may extendfor several years.

It is apparent, therefore, that during these extended periods ofstorage, it is necessary to protect the engine parts from rusting andother types of corrosion. ,Although numerous rust preventivecompositions have been suggested in the prior art, they have for onereason or another not been entirely adequate to satisfy all of therequirements which are desired. More specifically, certain prior artrust preventives, although providing adequate rust and corrosionprotection, have required considerable effort and delay in their removalfrom the engines prior to the reuse of these engines because of theirthick consistency. On the other hand, prior art formulations which areadapted to be readily removed from the engine prior to reuse, or whichare not required to be removed prior to reuse, are generally of a thinconsistency and therefore tend to drain from the engine parts on storageand thus leave portions of the engine unprotected, resulting in rustingand other types of corrosion.

A novel lubricant composition has now been found which acts as an enginelubricant at normal engine operating temperatures and which gels to aplastic-type rust preventive upon cooling. This novel composition of thepresent invention comprises a major proportion of a mineral lubricatingoil, about 1 to by weight based on the total composition of an organicpolymer having viscosity index improving properties, the combination ofsaid lubricating oil and said polymer having a viscosity in the range ofabout 90 to 150 SSU at 210 F., about 6 to by weight based on the totalcomposition of a micro-crystalline wax having a melting point in therange of about 155 F. to 205 F., and about l to 6% by weight based onthe total composition of a rust inhibitor.

In utilizing the lubricant composition of the present invention in anaviation engine, the lubricant composition is added to the aviationengine after removal of the bulk of the normal or regular aviation oilfrom the engine crankcase. The aviation engine is then run for a shortperiod of time to assure distribution of the lubri:

cant composition throughout the engine. Thereafter, the aviation enginecrankcase is drained to remove the bulk of the lubricant compositiontherefrom. It will be understood that a suflicient quantity ofthelubricant composition adheres to the engine parts so that upon cool2,843,548 Patented July 15, 1958 ing, the novel composition of thisinvention gels to a plastic-type film or coating.

The lubricant composition of this invention exhibits a number ofoutstanding features. To begin with,lupon cooling, the plastic-type filmcovering the engine parts remains as such indefinitely and does notdrain away or evaporate, which would result in exposure of variousengine parts. The protective film of the lubricant composition protectsthe engineparts not only from rusting but also prevents other corrosionsuch as that which might occur from traces of brominated scavengingagents remaining in the engine. The lubricant composition of thisinvention retains the property of setting to a gel even if diluted withlarge portions of a regular aviation oil. Thus, when the presentlubricant composition is employed in aviation engines, it is unnecessaryto remove the regular aviation oil completely prior to the applicationof the present composition. Another feature of the present lubricantcomposition is that the protective film which is formed does not gel tosuch a thickness as would require its removal prior to reuse of theaviation engine. In addition, the lubricant composition of thisinvention is compatible with a regular aviation oil and is also itself alubricant at normal aviation engine operating temperatures. Thus when itis desired to re turn the aviation engine to service, all that isrequired is to add the regular aviation oil to the engine crankcase.

The mineral lubricating oil employed as the major proportion] of thelubricant composition may be a. straight mineral lubricating oil ordistillate derived from parailinic, naphthenic, asphaltic, or mixed basecrude, or, if desired, various blended oils may be employed as Well asresiduals, particularly those from which asphaltic constituents havebeen carefully removed. An especially preferred lubricating oil is ablend of a distillate oil and a residual oil. The oils may be refined byconventional methods using acid alkali and/or clay or other agents suchas aluminum chloride, or they may be extracted oils produced, forexample, by solvent extraction with solvents of the type of phenol,sulfur dioxide, furfural, dichloro methyl ethyl, nitro benzene,crotonaldehyde, etc. The mineral oils may also be dewaxed by suchmethods as pressing and solvent dewaxing with methyl ethyl ketone,propane, etc. Hydrogenated. oils or white oils may be employed as wellas synthetic oils prepared, for example, by the polymerization ofolefins or by the reaction of oxides of carbon with hydrogen or by thehydrogenation of coal or its products.

Generally, the lubricating oil portion of the lubricant composition willrepresent about 69 to 92 Weight percent of the total lubricantcomposition. The viscosity of these lubricating oils will generally bein the range of about to SSU at 210 F. and preferably the lubri eatingoil constituent has a viscosity'index of at least about 85. 1

The organic polymers having viscosity index improving properties areemployed in the present lubricant composition in an amount in the rangeof about 1 to 10% by weight based on the total composition, andpreferably theV. I. (viscosity index) improver is employed in an amountin the range of about 8 to 10% by weight based on the total composition.A preferred viscosity index improver is a high molecular weighthydrocarbon such as an olefin, including the polymerized C to C olefins.For example, polymerized butenes and preferably polymerized isobutylenehaving a molecular weight in the range of about 5,000 to 50,000,preferably about 10,000to 20,000, are useful. These polymerized olefinsare readily prepared by procedures well known to the :art. Otherviscosity index improvers include the polymethacrylate esters,furnarate-vinyl acetate copoly mers, polyalkylstyrenes, and the like.

he combination of the lubricating oil and the V. I. im-

prover, in proportions the same as those employed "in the totallubricant composition, should have a viscosity in therangeof about 90.to 150 SSU at 210 F. This particular viscosity rangeis critical foraviation engine operation and is necessary inorder to assure theoperability of'the. lubricant composition in an aviationengine atoperating engine temperatures. If, however, the composition of thisinvention is to be. employed in engines otherthan aviation engines, itis possible to have a lower or-higher viscosity for the oil-V. I.improver combination than the range of 90 to 150 SSU at 210 F. set outabove.

The thickener employed in the lubricant composition of this invention'isa micro-crystalline wax having a melting point of about 155 F. to 205'F. The micro-crystalline wax is employed in an amount in the lubricantcomposition in the range of about 6 to 15% by weight based on -theJtotalcomposition and is preferably employed in therange of about 6 to 8% byweight. Preferably the higher melting point micro-crystalline Waxes,namely, those havinga melting point of about 170 F. to 205 F., areemployed in this invention.

Micro-crystalline wax is obtained from the dewaxing of residual oilssuch as bright stocks and cylinder oils and is distinguishable fromcrystalline wax which is derived from the dewaxing of predominantlydistillate lubrieating oil fractions. Crystalline wax generally has amelting point below about 150 F., whereas micro-crystalline wax isgenerally considered to have a melting point above about 155 F. Ingeneral, micro-crystalline wax is produced-by de-oiling motor oilpetrolatum obtained from the solvent dewaxing of residual oils such asbright stocks and cylinder oils. This de-oiling process, which removescertain low melting point wax constituents as well as the oil from themicro-crystalline wax product, is well known in the art and may beconveniently carried out at low temperatures employing a solvent such aspropane. A number of micro-crystalline wax products are availablecommercially and are sold under trade names such as Tervan 2536, Crown180, etc.

A number of rust-inhibiting materials may be incorporated into thelubricant composition of this invention .in an amount in the'range ofabout 1 to 6% by weight based on the total composition. Examples of suchrust preventives include the partial esters of polyhydroxy compoundssuch as the oleate of sorbitan, polyglycerols,

pentaerythritol, etc.; lauryl mercapto-acetic acid; ditriricinoleates;alkyl phosphoric acids; acid phosphates; fatty acid amides such as themono fatty acid amides of polyamines, e. g., the amides of fatty acidshaving 12 to 22 carbon atoms per molecule such as lauric, myristic,stearic, oleic, behenic,-etc., and amines such as ethylene diamine,propylene diamine, diethylene triamine, etc. pe-

troleum sulfonates such as calcium petroleum sulfonate,

barium petroleum sulfonate, etc. It will be understood that mixtures ofsuch rust inhibitors may also be employed in the present compositions aswell as the individual compounds. Sorbitan monooleate and the oleic acidamide of ethylene diamine having the formula where RC is derived fromoleic acid, are-especially preferedas rust inhibitors in the presentlubricant compositions.

Other agents than those that have been mentioned above may also bepresent in small amounts in the lubricantucompositions, such as dyes,color stabilizers, antifoaming agents, oiiiness agents, pour depresants,extreme pressure agents, and the like.

The following specific examples of this invention are presented to setforth the invention in greater detail, but itwill'be understood that itis not intended that they limit-the invention in any way.

EXAMPLE I A number of lubricant compositions were prepared and tested todetermine their suitability for use in aviation engines as lubricatingoils having the desirable characteristics set forth heretofore. Each ofthe lubricant blends in this example contained a lubricating oil and amicrocrystalline wax, and several of the blends, in addition, containedaviscosity index improver which was a polyisobutylene having a'molecularweight of about 14,000. In thisseries of experiments, the blends did notinclude a rust inhibitor since characteristics other than rustprevention were being evaluated specifically.

The following base oils were employed in this series of experiments:

Base oil A.This base oil wasa naphthenic-type mineral oil having aviscosity of 38.4 SSU at 210 F.

Base oil B.-This base oil was a naphthenic-type mineral oil having aviscosity of 75.2 SSUat 210 F.

Base oil C.-This base oil was a blend consisting of 50.0 volume percentof base oil B and 50.0 volume percent of a heavy bright stock having aviscosity of 210 SSU at210 F.

Base oil D.This base oil was a blend of 48% vby weight of 'oil I,whichwas a dewaxed distillate mineral lubricating oilhaving a viscosityof about 50 SSU at 210 F., and 52% by weight of oil II, which was adewaxed cylinder oil having a viscosity of about 210 SSU at 210 F.

Base oil E.This base oil was a blend of 60% by weight of oil I and 40%by weight of oil II, which oils have been described above under theheading base oil I Test 1.SSU viscosity at 210 F.

It was necessary that the blend of the base oil and the V. I. improverhave an SSU viscosity at 210 F. in the range of to 150 in order for thelubricant composition to be used as a lubricant at operatingtemperatures inian aviation engine. Blends not meeting this particularspecification would have to be removed from the engine prior to placingthe engine back in service.

Test 2.Apparent viscosity at 0 F.

The apparent viscosity at 0 F. measured in poises at 20 sec. shear ratewas determined in order to determine if the lubricant composition wouldbe so viscous after extended periods of storage that the lubricantcomposition would have to be completely removed from the engine prior toplacing the engine back in service. An

apparent viscosity at 0 F. ofless than about 6500 poises is consideredpassingin this test.

Test 3.-Flow test This test was carried out by diluting the lubricantcomposition with an equal volume of a regular commercial" aviation oil,heating the mixture to 205 F. in a test jar for fiveminutes, cooling thecontents .of the test jar to F., and then placing the jar on its side.No flow of.;the contents of the jar in ten'seconds passed this test.This particular test indicates the suitability of the lubricantcomposition for addition to engines containing retained regular aviationoil, since lubricantcompositions assesses failing this test would tendto drain from the engine parts The results of these tests as shown inTable III indicate on storage and leave portions of the engineunprotected. that composition A and composition B are excellent rust Thefollowing blends were prepared and gave the folpreventive aviation oils.It? ore specifically, it will be lowing results in the aforementionedtests: noted (1) that their viscosity is such that they may be TABLE IBase 011 in Blend Wax in Blend Apparent SSU at Vis. of Percent 210 F. ofBlend at Flow Blend VI Im- Base Oil 0 F. Test Type Percent prover PlusVI Type Percent (Poises of Blend in Blend Improver of Blend at secrlshear rate) A 90. 0 38. 4 A 10.0 150 Pass. B 95. 0 75. 2 A 5. 0 3, 600Fall. B 90. 0 75.2 A 10. 0 7,100 Pass. 0 90. 0 110. 5 A 10. 0 16, 000Pass. D 81. 0 152. 3 A 10.0 6, 100 Pass. D 85. 5 120. 7 A 10. 0 e, 200Pass. E 81.0 123. 7 B 10. 0 4, 000 Pass. E 84. 6 123. 7 B 0.0 4, 000Pass.

1 Iolyisobutylene (M. W.=approx. 14,000).

EXAMPLE I1 employed as engine lubricants at normal engine operatingtemperatures; (2) that their low temperature properties are such thatthey will remain as a plastic film protecting the engine parts overextended periods of time without The following two compositions wereprepared in accordance with the present invention:

TABLE H draining and yet not he so thick and viscous that they need beremoved from the engine parts prior to reuse q igg ggg ggflfig gg g ofthe engine; and (3) that they provide excellent rust Componentprevention and corrosion prevention properties.

What is claimed is:

An aviation engine lubricant composition consisting essentially of about79 wt. percent of a base oil, obtained by blending 60% by Weight of adewaxed distillate mineral lubricating oil having a viscosity of 50 S.S. U. at 210 F., and by weight of a dewaxed cylinder 0 oil having aviscosity of about 210 S. S. U. at 210 5.; 100.0 100.0 about 9 wt.percent of polyisobutylene having a molecular weight of approximately14,000, the combination of said These two compositions were evaluated iTests 1, 2, mineral lubricating oil and said polyisobutylene having and3, and were further evaluated in the following tests. 40 a ViSCOSit? ofabout 5- fi 5 7 percent 0 a microcrysta ine wax aving a me tin oint Testhumldlty cabinet test of about 189 F. obtained by de-oiling petrolatui npro- This test is carried out by dipping polished steel panels ducedfrom solvent dewaxing of cylinder oils and bright Composi- Composi- 3OtionA tionB Base Stock E 79. 0 Polylsobutylene (M. W.=approx. 14,000) 9.0 Wax B 7. 0 Sorbttan Monooleata. m. 5 Olelc Acid Amide of Ethylene Dmine in the lubricant compositions at 205 F., storing 4 hours stocks;and about 5 wt. percent of sorbitan monooleate. at 77 F., and 20 hoursat 140 F., and placing the dipped steel panels in a humidity cabinetmaintained at a teme rences Cited 1n the file of this patent perature of120 F. and humidity. UNITED STATES PATENTS Test 5.-HBr neutralizationtest 2,340,995 sn'lyers 8 1944 This test was carried out by dipping apolished steel 2,403,293 Mlskel y 2, 1946 panel in an emulsion of 10% byvolume of a 0.20% HBr 5 2,564,423 Barfmm 14, 1951 aqueous solution in aregular aviation oil, then dipping 2,632,709 Schlermelel' 24, 1953 thesteel panel in the lubricant composition for 1 minute, 2,648,643 Adams11, 1953 draining for two hours, and subsequently hanging the 2,716,611Paxton Aug 30, 1955 steel panel in a humidity cabinet maintained at 100%humidity and F. for 24 hours. No rusting passed 55 this test. Thefollowing results were obtained in these five tests:

TABLE III Test Oomposl- Composl- 50 tionA tlonB 1. S. S. U. at 210 F. ofBase Oil plus VI Im- 3. Flow Test 4. Humidity Cabinet Life (Hours) 5.HBr Neutralization Test Pass Pass

